Study On Service Oriented Distributed Operating System And Key Issues In Service Composition

With the technology development and progress such as programming paradigm, distributed computing and business computing, SOA (Service-Oriented Architecture) and SOC (Service-Oriented Computing) has got marked progress. More and more academics and industries are paying good deal of attention to this research field. Differenced from previous tightly coupled distributed computing technologies and software architectures, such as DCE, CORBA, DCOM, and EJB/J2EE, SOA presented a unified loosely coupled software architecture in which the computing resources are organized as "services".At present most of the abovementioned previous distributed computing technologies are trying to implement their cross-architecture, cross-company business integration based on "services", so that the heterogeneous systems can be interoperated with each other via a unified "service" platform, and the legacy systems can also be used continuously. But so far it seems that there is no operating system which can support SOC directly and effectively.In this dissertation, the architecture of current SOA applications is analyzed firstly. We notice that current abstraction of "service" is only at middle level of the SOA application architecture, and is still based on the traditional process/thread abstractions. So, here are the coming questions, "Can operating system support SOC directly and effectively", "Can operating system be directly interoperated with each other or with other distributed computing systems via the unified service abstraction"? To these goals, the dissertation made systemically and deeply study on how to building service oriented operating systems.The critical and significant problem of building service oriented operating system, whether distributed or not, is to construct the abstractions of services at the operating system level. Therefore, we introduce the service concept into the basic abstractions of operating system, and then lead the concepts into SEFM, an operating system construct model presented by professor Gong YuChang, etc. in USTC. In the extended SEFM, the servant is the carrier of the services; the port is the communication and access interface of the services; and the subport is the service instance.To construct SODOS, the service oriented distributed operating system, some other key issues are studied and discussed in detail, including the architecture of SODOS, the service interface with single system image, the publishing of services, the proxies of remote service request, naming and name services, scheduling method of multiply execution flows, the migration of service copies and service instances and the consistence maintaining, etc.Besides the construction of SODOS, for SOA applications, the deployment of the basic services and the method of service composition path selection are also very important. At present, most studies are for large-scaled networks such as internet, service grid and service overlay network, but not for LDS-env (a kind of Local and Dense Services environment) in which the characteristics of deployment and communication are much different. Therefore, two algorithms, a static service deploying algorithm and a service composition path optimizing algorithm, are proposed, analyzed, simulated and improved.The contributions of the dissertation are listed as follows:·It is the first time to introduce the concept of service into the abstractions of operating system, and to lead the concept into SEFM, a novel construction model of operating system.·It is also the first time to propose service oriented operating system, whether distributed or not. The architecture and some other key issues of SODOS were studied, discussed and solved.·For SOA applications, a static service deploying algorithm over LDS-env are presented, simulated and improved, considering the network traffic, load balance, service distribution degree and fault tolerance.·Also for SOA application, a service composition path optimizing algorithm over LDS-env are presented and simulated, considering the path length optimizing and load balance.